PROJECT SUMMARY The ultimate goal of the proposed work is to develop a novel co-formulation of insulin analogues (e.g. lispro and aspart) with an amylin analogue (e.g. pramlintide) to enable a transformational new treatment for diabetes constituting a true replacement therapy. The most challenging aspect of optimal glycemic control for the 1.25 million people with type 1 diabetes in the United States is limiting large increases in blood glucose after a meal. People with type 1 diabetes do not produce the insulin required for the body to process glucose, so insulin must be replaced by daily injections. Amylin is a small peptide hormone excreted alongside insulin by pancreatic ? islet cells that acts centrally to slow gastric emptying, suppress postprandial glucagon secretion, and decrease food intake, thus complementing the action of insulin to regulate blood glucose levels. Similar to insulin, amylin production is completely absent in individuals with type 1 diabetes on account of their lack of pancreatic ? cells. While treatment of diabetes with a combination of insulin and amylin analogues at meal times has been shown to be more effective than insulin alone, the burdensome administration of insulin and amylin analogues as two separate injections since these proteins can't be co-formulated. Symlin (Pramlintide; AstraZeneca), the only commercial amylin analogue formulation, is formulated at pH~4 while Novolog (Aspart; Novonordisk) and Humalog (Lispro; Eli Lilly), insulin analogue formulations, are typically formulated at pH~7.4. We have developed an approach to non-covalent PEGylation of proteins enabling stable co-formulation of these two drugs for the ?rst time whereby their optimal therapeutic ratio is de?ned in the formulation. This novel combination therapy will yield unprecedented postprandial glycemic control and catalyze the development of a powerful tool for the management of diabetes affording thus far unrealized therapeutic impact.